Render is much faster when laptop is plugged in and charging
Your issue lies in power management.

Your operating system (Windows 10) is currently instructed to limit performance of your CPU and GPU and in order to save power and extend battery life and longevity.

It sucks.

How to fix it:


Navigate your way to Control Panel
Go to System and Security
Go to Power Options
Go to Change Plan Settings
Choose Advanced Power Settings
Verify that minimum processor state and maximum processor state are set to 100% all the time
Set cooling policy to active
Disable PCI Link State Power Management


I don't have Nvidia graphics, so I can only assume there is a power management section in the NVidia Geforce Experience or something


Since you're on a laptop, you should also buff up your integrated graphics as the data from your 2060 may or may not be passed through the integrated graphics card.
Follow the BlenderGuru's advice to speeding up Cycles rendering in general. 
https://www.youtube.com/watch?v=8gSyEpt4-60 
Update your drivers if needed.